1. Field of the Invention
The present invention relates to a novel method for improving memory of objects, events, and the like and cognitive functioning related to the objects, events, and the like for the human brain by measuring, determining, recording, and correlating object-related, event-related, recall-related electrical brain potentials ("ERP") with the use of whole skull electroencephalography, using a disposable electrode cap connected to a computer system arrangement and more particularly to a method of measuring and determining a large number of meaningful brain electrical potential changes in response to a continuously presented and varied specific verbal stimulus or verbal stimnuli interspersed with non-significant verbal stimuli concerning memory of objects, events, and the like and cognitive functioning related to the objects, events, and the like by a subject to establish an actuarial or historical base line for use within a predetermined time period and analyzing the measured ERP responses against the historical base line established from the related ERP data established from a group defined as a normal to coaching or feedback to the subject either as a non-verbal (e.g. manual) response or verbal response within the predetermined time period, using a computer.
2. Description of the Prior Art
The research in the area of cognitive functioning and brain physiology is of two general types, blood flow related and electrical activity. The blood flow type studies can employ different types of measures, including, oxygen, glucose or neurotransmitter use as well as other variations. Methodologies include the PET scan, SPECT scan, MRI, etc. Toga, A. W., & Mazziotta, J. C. (1996) have outlined the science and methodology of these and additional approaches of optical imaging, ERP's and transcranial stimulation. Studies of electrical activity will address event-related potentials (ERP) or quantitative EEG measures. ERP's study the activity of the brain within milliseconds following exposure to a stimulus. QEEG studies employ a longer period of time for analysis. The relationship between blood flow and electrical activity has been researched with varied findings. One study indicated that low blood flow is reflected in discordance in the theta (4-8 Hz) and beta (12-18 Hz) bands (Leuchter, A. F., Cook, I. A., Lufkin, T. B., Dunkin, J., Newton, T. F., Cummings, J. L., Mackey, J. K. & Walter, D. O. (1994)). Discordance was a measure developed which analyzes the relationship between relative and absolute power of a bandwidth. However, Leuchter et al. also noted that the associations between EEG power and perfusion or metabolism vary considerably across frequency bands and sites, with some studies showing little or no association.
Hemler, R. J. B., Hoogeveen, J. H., Kraaier, V., VanHuffelen, A. C., Wieneke, G. H., Hijman, R., & Glerum, J. H., (1990) were able to demonstrate that a 60% decrease in blood flow (induced by Indomethacin) resulted in a -0.3 Hz slowing of the alpha (8-13 Hz) peak frequency and a decrease in the relative power of the alpha band. There were no chances in the delta or theta band but there were decreases on memory performance tasks under the low blood flow condition. Jibiki, I., Kurokawa, K., Fukushima, T,. Kjido, H., Yamaguchi, NJ., Matsuda, H., & Hisada, K., (1994) were able to obtain significant negative correlations between blood flow (in group of patients with partial epilepsy) and the relative power of theta (4-7.8 Hz) and a positive correlation between blood flow and alpha (10-12.8 Hz) in the frontal, parietal and temporal regions. In the occipital regions there was a positive correlation between blood flow and relative power of beta1(13-25 Hz). The authors also noted that in previous research there was supporting evidence for the inverse relationship between delta and theta activity and blood flow (studies with cerebral infarction, Alzheimer's, and Pick's disease) as well as positive correlations between alpha power and blood flow.
For both types of methodologies the issue of location is paramount. Blood flow type studies generally employ a longer period of time for analysis, as the technology requires it, while RP studies focus in the millisecond range. QEEG studies will study seconds, not milliseconds. Blood flow studies focus on the difference between the activity under investigation and a control condition, which can be eyes closed or another relevant activation condition. ERP measures employ more of a level, location and time analysis. For example, a response to a stimulus is indicated by time since onset of stimulus, level of amplitude of response, and location of response. Electrophysiological studies enjoy the more precise measurement of the time variable and bypass the problem of the subtraction method. The subtraction method employs two conditions and subtracts the activation in one condition from the activation in another. The result is a degree of activation ditference measure (as indicated by t-tests). This methodology has received criticism due to the difficulty of assuming that its operational assumptions are valid. The discussions of these problems are evidenced in Price, C. J., Moore, C. J., & Friston, K. J. (1997)) and Friston, K. J., Price, C. J., Fletcher, P., Moore, C., Frackowiak, R. S. J., & Dolan, R. J. (1996).
Many studies in this area will focus on pathological states, i.e. Alzheimer's, and will look for differences with normals or activity of the pathological condition. Very few studies have looked at either the degree of activation from an appropriate condition or absolute level in terms of the effectiveness of cognitive functioning. The main emphasis has been on what happens where when we do this. The main cognitive correlates which have been studied include such activities as memory, reading, face recognition, etc.
Theoretical approaches to the understanding of brain dynamics and function have been of five general types. The first type as exemplified by Roland, P. E. (1993) can be described as a modular type, as it indicates what region is activated for a given task. Per Roland describes his approach as the cortical field activation hypothesis. "The cerebral cortex participates in brain work in awake human subjects by activating multiple cortical fields. Each activated field has an area of a few square centimeters. Activation means that the synapses and neurons in a field increase their biochemical activity. This leads to increases in transmembraneous ion transport and in increases in the rate of the regional cerebral metabolism (rCMR) or regional cerebral blood flow (rCBF) . . . The hypothesis states that the neurons in the cerebral cortex always chance their biochemical activity, not in a scattered and singular fashion, but in large distinct ensembles, each covering some 800 mm.sup.3 to 3,000 mm.sup.3 of the cortex." (Roland, 1993, p. 105)
The second approach is an interactive-regional one, where different regions arc presumed functionally linked for a particular task. Gevins, A., Cutillo, B., DuRousseau, D., Le, J., Leong, H., Martin, N., Smith, M. E., Bressler, S., Brickett, P., McLaughlin, J., Barbero, N., & Lazer, K. (1994) employed a Evoked Potential Covariance measure and conclude that their results suggest the concept of functional networks in that each component cognitive process is associated with a sequence of spatiotemporal patterns of coordinated processing involving widely distributed areas of sensory, association and motor cortices. McIntosh, A. R., Nyberg, L., Bookstein, F. L., & Tulving, E. (1997), (p. 323) expand on this type of analysis in maintaining that "One way to examine whether the same region has a consistent pattern of interactions across retrieval tasks is to explore change in "functional connectivity", loosely defined as the correlation of activity among brain regions . . . the neurobiological interpretation of functional connectivity is simply that two or more regions show correlated activity without reference to how the patterns may be mediated. Further elaboration requires more explicit models to determine the effect regions have on one another, or "effective connectivity"."
The third approach, the flebbian approach is exemplified in some of the research. D. Hebb proposed that knowledge is represented by a collection of neurons, which act as a unit and are required to be activated as a unit for accurate processing. The emphasis on cell assemblies is the theoretical explanation provided for an understanding of the results of Pantev, C. (1995) who maintained that the relationship of rapid (100 ms) event related gamma activity (30-110 Hz, depending upon the stimulus and location) are the activity of the synchronized cell assemblies that are discussed by D. O. Hebb. As an offshoot of the Hebbian concepts, there has also been considerable focus on Neural Network Theory and development (Arbib, M. A.(Ed.) (1995)). This approach attempts to specify the exact nature of the Hebb theory of synaptic change and learning.
In a similar vein "Damasio (1989) made an attempt to integrate findings . . . in his theoretical framework the subcortical structures still have their place for memory functions, however, they are only kind of relay stations which enable storage and retrieval, and do not contain engrams which are assumed to be located in the cortex. However, there they are not stored as holistic units in narrowly circumscribed regions, for example as "grandma cells", but rather was sets of representational fragments in multiple and separate regions. A memory content is accessed if these representational fragments are triggered either by perceptual input or by active memory search. In each case triggering means that the very same activity pattern is recreated in the distributed cortical cell assemblies which was venerated originally, when the entity, a face, etc. was first encountered." (Rosler et al, 1995, p. 301) Damasio (1989) elaborates on this approach by emphasizing that recall of entities and events "1--are activated in time locked fashion; synchronous activations are directed from convergence zones . . . and the process of reactivation is triggered from firing in convergence with and mediated by feedback projections. This proposal rejects a single anatomical site for the integration of memory and motor processes and a single store for the meaning of entities and events. Meaning is reached by time-locked multi-regional retroactivation of widespread fragment records. Only the latter records can become contents of consciousness." (p. 25) Damasio's emphasis upon time locked regional activations places the emphasis upon activated areas. Although he speaks of projections, these projections provide the impetus for activation and are not the focus of recall. For example, he states that "consciousness emerges when retroactivations attain a level of activity that confers salience." (Daamasio, p. 54).
The fourth approach has focused on the electrophysiology of memory and is best exemplified by the research conducted by Klimesch, W., (1996). He notes previous research relating decreased alpha frequency to decreased memory performance in Alzheimer's disease. Klimesch has proposed an integrative memory model, which integrates cognitive psychology, neuroanatomy and neurophysiology and focuses his research and conclusions on variations in synchronizations in the theta and alpha frequency. He defines type 1 synchronization as involving large cortical areas reflecting mental inactivity and type 2 synchronization as the "regular synchronous oscillatory discharge pattern of selected and comparatively small cortical areas" (p. 81). He further elaborates that "the synchronization of very large populations of neurons oscillating with the same phase and frequency reflects a state in which no information is transmitted" (p. 81). He adds "regular type 2 synchronization is that specific oscillatory mode in all of the frequency bands that reflects actual information processing in the brain (p.82)". He further differentiates between low alpha (7-11 Hz) and high alpha (10-13 Hz) and relates desynchronization in these different bandwidths to effective memory performance. His conclusions state that "short term (episodic) memory processes are reflected by oscillations in an anterior limbic system, whereas long-term (semantic) memory processes are reflected by oscillations in a posterior-thalamic system. (p. 61)" The relationship to this patent is that he claims that he focuses on individual alpha frequencies as important to memory (with good memory performers having 1 Hz or higher frequencies), bad memory performance is relate to "a weak or insufficient desynchronization of the lower alpha band. (p. 71)", that alpha is the dominant rhythm reflecting long, term memiory processes . . . hippocampal theta rhythm may reflect the encoding and retrieval of episodic information in working memory (p. 76)." He relates synchronous activity (with implied increased phase relationships) to mental inactivity when he states "the synchronization of very large populations of neurons oscillating with the same phase and frequency reflects a state in which no information is transmitted. (p. 81)." He adds "regular type 2 synchronization is that specific oscillatory mode in all of the frequency bands that reflects actual information processing of the brain (p. 82)." Thus high phase relationship (and presumably high coherence relationships) across broad, long distant relationships in the brain are reflective of low/no information transfer.
A related electrophysiological theory of brain functioning is proposed by Thatcher, R., Krause, P. J., & Hrybyk, M. (1986) where a two compartment model which indicates two separate sources of EEG coherence. The first is coherence produced through the action of short length axonal connections (gray matter connections) and the second is coherence produced through the action of long distance connections (white matter fibers).
The fifth approach has been the employment of the hologram as a theoretical metaphor for brain functioning (Pribram, K., 1994). The optics of hologram science, as put forth by Collier, R. J., Burckhardt, C. B., & Lin, L. H., (1971), indicate that a hologram requires a coherent light source reflecting off both a pure reflecting object and a subject and both reflected back to a recording medium. "Holography is an interference method of recording the light waves diffracted by a subject illuminated with coherent light. The diffracted waves are caused to interfere with a phase-related reference wave. If the waves are highly coherent, the relative phase between subject and reference wave remains constant in time producing an observable effect on the intensity distribution of the resulting interference pattern. The photographic record of this pattern, the hologram, contains sufficient information about both the phase and amplitude of the diffracted waves to permit their reconstruction . . . preservation of relative phase information in a retrievable form between the two sources of information which is recorded onto the medium and allows the creation of a hologram." (Collier, 1971, p. 3)
The theories are generally linked to the type of data they are collecting. For example, blood flow studies indicate locations as results. Thus a theory which attempts to explain blood flow results must necessarily focus upon regional activation, as the data presents itself in this format. The more advanced level of theoretical organization with this type of data is the functionally related orientation. ERP studies will also focus on location and connectivity. QEEG studies also can more appropriately address issues of connectivity and function, as the variables of coherence and phase allow this type of theorizing. QEEG studies, however, can also effectively address issues of activation, as indicated in the measures of magnitude, relative power, etc. Thus the QEEG can allow the integration of activation and connection concerns in theoretical construction of brain dynamics.
A related issue in this discussion is the mind body problem and the level of analysis. These issues come out of the area of the philosophy of science. The studies addressing brain function are generally correlating physiological measures with psychological measures. The two problems here are 1--correlation cannot be inferred to indicate causation and 2--explanation on one level of scientific analysis cannot be employed easily to explain events on a different level of analysis. For example, although we can identify/correlate physiological correlates of fear or love, have we explained these emotions by use of these variables. Each scientific area of study employs certain constructs and operational variables in its study and analysis. To jump across levels of analysis without solid empirical links is an inappropriate theoretical endeavor. Translation of a phenomena to a different level of analysis loses information which is embedded in the original level of analysis. For example, fear and love are psychological constructs, not physiological constructs. Thus we can correlate physiology with psychology, but we cannot say, for example, that increased heart rate is fear.
Within the field of biofeedback applications to problems in human functioning, there is a subspecialty, commonly referred to as Neurotherapy. Neurotherapy is the providing of electrophysiological information (in the form of the QEEG parameters) to a subject for the purpose of changing the parameter being measured. This type of biofeedback has been successfully employed in the remediation of Attention Deficit Disorder (Lubar, J. O., & Lubar, J. F. (1984)(N=6)), the elevation of IQ scores 15 to 25 points (Tansey, M., (1991) (N=21), Othmer, S. & Othmer, S. F., (1992)), addictive conditions such as alcoholism (Peniston, E. G. & Kulkosky, P. J., (1990)(N=30)) and emotional problems such as depression and anxiety (Peniston, E. G., (1993), Peniston, E. G. & Kullkosky, P. J. (1991)) in Veterans (N=20). Peniston (1993) employed an increased theta/decrease alpha protocol at the occipital and frontal positions to induce abreaction.
While these results have been empirically impressive, they have not been based upon a complete theoretical orientation and/or empirical base of brain physiology. The research has primarily focused on the C3-Cz locations (ADD and Learning Disabilities) and occipital leads (alcoholism) and have addressed issues of reducing theta and/or increasing alpha or beta activity (depending upon the problem). None of the research to date has examined or attempted to address the issues of rehabilitation with the coherence and phase relationships.
The research conducted for this patent was explicitly designed to address the whole brain's effective electrophysiological response to specific cognitive tasks. It was the thinking of the inventor that only by studying the problem in this manner can we obtain the findings that are relevant for the Neurotherapy situation. Specific answers to specific questions can allow specific interventions for specific problems in the areas of cognitive rehabilitation as well as increasing cognitive abilities in normal subjects. The fields of application for the findings not only include all rehabilitation facilities engaged in cognitive remediation, all school systems with learning disabled children and Attention Deficit disorders, all mental conditions which have a cognitive component, as well as the general public who might wish to "tune up" their brains. The knowledge presented in this patent application can potentially revolutionize the field of education and cognitive rehabilitation as well as offer to the general public a significantly effective method to improve mental functioning in the workplace, and thus improve the competitive edge of businesses.
Specific Findings Regarding Memory Functioning and Brain Physiology
Findings generated from the blood flow type research are relevant but not particularly prior knowledge with respect to this patent application. This is because 1--blood flow measures are not electrophysiolog,ical measures and 2--the relationship between blood flow measures and electrophysiologyical ones is only partly defined one at present. Therefore, even though a blood flow study may indicate activation in a region for a particular task, it is not a prior knowledge that this finding necessitates a certain type of electrophysiological activity in that region because of that blood flow fiinding. In addition, blood flow studies tell us nothing about connectivity. Thus all blood flow type research is irrelevant to the domain of this patent application. In addition, all Event Related Potential research fails to constitute prior knowledge in this area for a different reason. ERP's study the subject's response in milliseconds. The relationship between activity in the first several hundred milliseconds of a response and the subject's response over a 30 second interval has not been addressed in any research. Although ERP research employs similar type of constructs, such as amplitude, coherence, etc. it is in a different the domain. Therefore all ERP research is irrelevant to the domain of this patent.
In terms of QEEG research, there are generally four types of research that are relevant to this patent.
1. Differentiating Clinical Conditions (i.e. ADD vs. Normals, Learning Disability vs. Normals) on the Basis of Eyes Closed Resting Condition Values
The connection in these studies is that, presumably, if a clinical population has differences in electrophysiological functioning then these differences are related to the known cognitive differences.
2. Activation Patterns Under Specific Task Conditions
Research in this are will indicate what happens when a subject reads. Although this approach can tell us what is involved in reading, it cannot tell us the difference between successful and unsuccessful reading (i.e. comprehesion/memory).
3. Analysis of Difference in Activatin/Connection Patterns to Success in Task Condition
This is the most relevant to the present patent application as it addresses the same problem. Studies in this area focus on degree and location of activation and/or connectivity patterns. The simultaneous combination of both of these types of measures is what is relevant to this patent.
4. Rehabilitation Efforts With Attention Deficit Disorders, Learning Disabilities and Other Clinical Conditions.
The ability to change electrophysiological parameters and demonstrate increased cognitive functioning is a strong argument for the causal effect of electrophysiological measures on cognitive measures. However, much of the research has not specified what the exact causal route is. The electrophysiological measures and cognitive measures employed have been broad measures. It would be more exacting to be able to state that electrophysiological variable X relates to cognitive variable Y and that if we change X we will find a change in Y.
5. Differentiating Clinical Conditions (i.e. ADD vs. Normals, Learning Disability vs. Normals, Clinical Conditions vs. Normals) on the Basis of Eyes Closed Resting Condition Values
While it is the case in first above described type of research that there certainly must be some connection between the eyes closed condition and activation conditions, there is no research, which specifically evaluates that relationship. The type of research conducted under this model includes Giannitrapani, D., (1985) had been able to relate performance on the WISC Arithmetic and Comprehension scores to (not in an activation procedure) to power in the low beta frequencies. Thatcher, R. W., Walker, R. A. (1985) related increased WISC IQ scores (intra-hemispheric analysis) to short inter-hemispheric connections, especially in the posterior regions. The best overall predictors of IQ (hemispheric analysis) were the coherence figures from the frontal and fronto-temporal regions. A multiple regression approach indicated interhemispheric coherenccs were better predictors of IQ than intrahemispheric coherence.
Fein, G., Galin, D., Yingling, C. D., Johnstone, J., Davenport, L., & Heron, J., (1986) (N=113) were able to consistently show decreased beta power (19-24 Hz) in dyslexics (eyes closed condition) but no differences in the other bands.
Harmony, T., Hinojosa, G., Marosi, E., Becker, J., Rodriguez, M., Reyes, A., & Rocha, C., (1990) (N=81) were able to identify children with poor educational evaluations on the basis of absolute power of delta (poor evaluations) and increased alpha at occipital areas (good evaluations). The relative power variables correlated more with the learning problems. Children with very poor evaluation had more delta activity in left frontal and temporal areas, while increased theta activity was found for children (matched for SES) who were lower on the educational evaluations than their matched peers.
Byring, R. F., Salmi, T. K., Sanio, K. O., Orn, H. P., (1991) (N=44) were able to differentiate between spelling disabled children and normals on the visual basis of excess slow activity (especially in temporal regions) and quantitative basis in terms of low alpha and beta powers, and high complexity (spread of frequencies) in the parieto-occipital regions in the spelling disabled children. The authors noted the inconsistent findings in previous research with dyslexics in terms of theta, alpha and beta activity.
Giannitrapani, D., Collins, J., & Vassiliadis, D., (1991) noted that in Alzheimier's and dementia patients there was an increase in slow activity and decrease in fast activity and that the differentiating characteristic on the non-Alzheimer's dementia was a decrease in the frequency of alpha activity.
Marosi, E., Harmony, T., Sanchez, L., Becker, J., Bernal, J., Reyes, A., Diaz de Leon, A. E., Rodriguez, M., & Fernandez, T. (1992) (N=152) were able to demonstrate different patters of maturation of the coherence figure in normal and learning, disabled children under the eyes closed condition.
Mann, C. A., Lubar, J. F., Zimmerman, A. W., Miller, C. A., & Muenchen, R. A. (1992) (N=25) were able to demonstrate increased amplitude theta activity (4-7.5 Hz) and decreased betal (12.75-21 Hz) (compared to normals) in ADD subjects when subjects were reading or drawing. The increased theta activity was more prominent in frontal regions, while decreased beta was significantly decreased in temporal regions. For children with dyseidetic disorders (difficulty with visual spatial processing for whole word recognition) there was increased left temporal theta in the t3-p3 region. Lubar, J. F., Bianchini, K. J., Calhoun, W. H., Lambert, E. W., Brody, Z. H., & Shabsin, H. S. (1985) had obtained similar results.
Leuchter, A. F., Cook, I. A., Lufkin, T. B., Dunkin, J., Newton, T. F., Cummings, J. L., Mackey, J. K., & Walter, D. O. (1994) (p. 208) noted that "pathologic slow waves in the 0-4 or 4-8 Hertz frequency range are known to be caused by partial deafferentation of the cerebral cortex. Deafferentation of the pyramidal cells in lamina II and III is the neurophysiologic principle unifying slow wave production due to tumor, infarction, ischemia, demyelination or degeneration. These cells are responsible for the generation of much of the normal brain electrical activity, and they produce slow waves only in response to a loss of afferent input." This type of analysis would indicate that delta/theta waves are correlated with low cognitive ability due to the loss of input.
Ackerman, P. T., Dykman, R. A., Oglesby, D. M., & Newton, J. E. O. (1995) (N=119) were able to show that dysphonetic readers had significantly higher values in the theta and delta bands. Both phonetic and dysphonetic poor readers had lower beta activity than Attention Deficit Disorder subjects with adequate reading skills.
Chabot, Merkin,Wood, Davenport, & Serfontein, G. (1996) (N=407) who were able to distinguish between normals and ADD/ADHD and Learning Disabilities on the basis of QEEG variables on the basis of coherence, relative power, asymmetry and location issues (eyes closed condition).
Evans, J. R. & Park, N. S., (1996) were able to identify siglificant deviations from a normative database in a group of 8 dyslexic children and 2 adults. These were evident in the left posterior region (in particular the P3 position) in terms of reduced coherences and usually involved the theta bandwidth.
Koyama, K., Hirasawa, H., Yoshiro, O., & Karasawa, A. (1997) noted that age had no effect on interhemispheric coherence but intrahemispheric coherence was found to decrease with age in all bands almost linearly and was a more sensitive indicator of normal aging than relative power.
In summary, this pattern of research findings implies that cognitive abilities reside in increased beta (13-21 Hz) activity, decreased theta and delta activity and increased coherences.
With regard to the aspect of research involving activation patterns under specific task conditions. Sklar, B., Hanley, J., & Simmons, W. W., (1973) (N=25) demonstrated that dyslexic children had more theta activity (3-7 Hz) in the parietal region (rest condition) as well as more activity in the 16-32 Hz range than normals, who had more 9-14 Hz activity (alpha). Under the reading task condition, however, the normals increased activity in the 16-32 Hz range, while the dyslexics decreased activity in this Hertz range. Within the same hemisphere, the coherences were higher for the dyslexics but lower between homologous connections (similar positions) across the hemispheres than normals (reflecting possible problems in the corpus callosum).
Gevins, A. A., Zaeitlin, G. M., Doyle, J. C., Dedon, M. F., Schaffer, R. F. & Yeager, C. L., (1979) and Gevins, A. A., Zaeitlin, G. M., Doyle, J. C., Schaffer, R. E., & Gallaway, E., (1979) found slightly higher theta spectral intensities in frontal and occipital cortex during serial addition, letter substitution and block rotation tasks.
Duffy, F., Denckla, M. B., Bartels, P. H., Sandini, G., (1980) (N=18) found differences between normals and dyslexics in terms of the bifrontal areas as well as the expected left temporal and left posterior quadrant. The activation tests produced more prominent group differences. Dyslexics were noted to have increased alpha during activation conditions (relative to controls).
Dykman, R. A., Holcomb, P. J., Oglesby, D. M., & Ackerman, P. T., (1982) (N=10) employed a complex visual search task and recorded over the central and parietal sites and were able to differentiate between the groups (hyperactive, learning disabled, mixed and normal children) on the basis of two frequencies--16-20 Hz and 7-10 Hz.
Grunberger, B. S., & Grunberg, J., (1985) were able to demonstrate that elderly subjects with poor memory exhibited slow activity and less alpha and alpha adjacent beta activity than elderly subjects with good memory.
Duffy, F. H., Denckla, M. B., McAnulty, G. B., & Holmes, J. A., (1988) were able to demonstrate increased alpha in dyslexics under rest and activation conditions as compared to normals in the left posterior, left anterolateral frontal, left midtemporal and bilateral medial frontal areas.
Gutierrez, S., & Corsi-Cabrera, M., (1988) (N=8) monitored EEG activity during spatial, verbal and one demanding mixed task to determine possible hemisphere and performance effects. They found no significant differences between performance levels but increased beta power in the left posterior region across all tasks, as well as decreased alpha relative power and increased theta relative power.
Randolph, C., & Miller, M. H. (1988) (N=20) examined head injured and normal subjects during several cognitive tasks and employing T3, F4, O1, & O2 electrode placements. They found significantly worse performance in the head-injured subjects and increased (in comparison to normals) EEG amplitudes and amplitude variances. They were able to correlate decreased performance with increased amplitude variances at the temporal lobes for 2 of the 4 cognitive tasks they administered.
Matsuoka, S.,(1990) examined the midline frontal theta and noted the clinical observation that there is the appearance of this theta activity under various conditions which include simulated driving, brain tumor, chemical intoxication, exercise, mental calculation sleep and meditation.
Galin, D., Raz, J., Fein, G., Johnstone, J., Herron, J., & Yingling, C., (1992) (N=113) concluded in an activation procedure for dyslexic and normal readers that the theta activity in the temporal lobes was the main discriminating variable between the two groups.
Valentino, D. A., Arruda, J. E., & Gold, S. M., (1993) conducted an auditory continuous performance task (N=27) and compared performance levels with EEG variables. They found an increase in beta power (especially in fronto-temporal and left temporal sites) decreases in alpha and posterior theta, and increased anterior theta and delta. The lower performing group had decreased left temporal heta power, while the good performers had, in addition, more anterior beta and less posterior alpha and theta.
Klimesch, W., Schimke. H., & Pfurtscheller, G., (1993) were able to show that during retrieval the alpha frequency (frequency range not stated) of good performers is 1.25 Hz higher than for bad performers. During retrieval, alpha desynchronization is more pronounced for bad performers than good performers. Special cognitive tasks such as reading, classification and recognition as well as attentional demands tend to reduce the power within the alpha band. They also noted that mental tasks and task difficulty in particular lead to an increase in alpha frequency but only for difficult but not for easy tasks. They also noted that alpha frequency increases selectively in that hemisphere which is dominant for a particular task.
Lutzenberger, W., Pulvermuller, F., & Birbaumer, N., (1994) were able to demonstrate significant differences in activation of the 30 Hz range in subjects between the presentation of words and pseudowords with words eliciting a synchronous activation of large cortical cell assemblies.
Klimesch., W., Schimke, H., & Schwaiger, J. (1994) employing an ERP methodology noted that semantic memory process are reflected primarily in alpha band and episodic memory is related to activity in theta band.
Fernandez, T., Harmony, T., Rodriguez, M., Bernal, J., Silva, J., Reyes, A., & Marosi, E. (1995) (N=25) analyzed the EEG up to the 19 Hz range in terms of the differences between the task conditions (subtracting 7s) and resting condition. They round significant differences in the delta (1.5-3.5 Hz) and theta (3.5-7.5 Hz) bands in the right posterior areas and in the beta (12.5-19 Hz) band in the frontal area.
Klimesch, W., Doppelmayr, M., Schimke, & H., Ripper, B., (1997) noted in another ERP study that episodic encoding and retrieval processes are primarily reflected by a task related increase in theta power. With subjects performed a recognition task the results indicated that only those words that were later correctly recogized produced a significant increase in theta power during the encoding stage. During the actual recognition processes there was significant theta synchronization (increase in band power) for correctly remembered words only. Employing an immediate recall procedure, they found theta relative power increases during the recall period.
Rosler, F., Heil, M., & Hennighausen, E., (1995) studied whether long term memory retrieval is correlated with specific changes in slow, DC like event-related brain potentials. The results indicated a positive relationship to slow negative shifts of 5-10 mV, which prevails about as long as the retrieval process lasts (several seconds). When different types of representations have to be reactivated in memory the slow negative wave shows a clearly distinct topography. The maximum was found in a verbal condition over the left frontal, in a spatial condition over the parietal, and in a color condition over the right occipital to temporal cortex. The amplitude of the topographic maximum increase with the number of representations which have to be reactivated.
Sterman, M. B., (1996) was able to relate (in an event related paradigm) decreased posterior 7-9 Hz at time of presentation (125-250 msec) to effective subsequent recall in a target recall task. At time of recall the ERD (event related desynchronization) was significantly increased (500-625 msec) for the good performers. This article is included to reflect at least one of the studies that have related ERP measures to performance.
Leuchter, A., (U.S. Pat. No. 5,309,923--May 10, 1994) employed a cordance method in analyzing the responses of 11 subjects (mixed group of 5 normal elderly, 4 major depressives, and 2 early dementia) during a memory task (analyzing 4 second periods). The subjects were show slides of pen and ink drawings of common objects for 5 seconds. QEEG data was collected during presentation. Subjects were asked to spontaneously recall the items at both a 3-minute lapse and again at 7 minutes post testing. Subjects were scored on their recall ability during both testings. Leuchter, A. pooled the recordings according to whether the objects were recalled later consistantly (both recall tests) or not at all (recalled at neither of the recall periods). The results were analyzed according to his cordance system and further scored in terms of their overall recall ability. He defines cordance by the relationship between the absolute power and relative power of a bandwidth. When these figures are not consistent (as defined by a midpoint or selected base) there is discordance. For example, when the relative power of alpha is high versus its selected base as well as its amplitude, then there is a condition of cordance. If Alpha relative power is high, but its amplitude is low, then discordance exists. In his study he demonstrated that the concordance of the Alpha frequency (8-12 Hz) in the left temporal lobe was associated with good visual memory performance.
The neurophysiologic activation pattern that was associated with (good recall involved the temporal regions (T3, T5 and T4, T6). A good memory performance was associated with left temporal concordance, while a poor performance was distinguished by a shift to the right temporal concordance. There was also evident a pattern of central discordance or deactivation for two of the good memory subjects. Further analysis by subgroup revealed some differences in cordance, memory and clinical condition, but which were interpreted in line with the general interpretation. He also noted a left/right ratio of Alpha power increasing during the task and that the subjects who failed to obtain this ratio, the memory performance was below the others. Lechter notes that cordance provides information on perfusion (blood flow activity) in that there is a strong relationship between mean perfusion and concordance in the Alpha frequency range.
Although Leuchter claims, in his patent, all possible frequency ranges, all possible time interval periods, channels up to 128, and also lays claim to voltage, amplitude and coherence values. Yet Leuchter only sampled up to 30 Hertz, examined the data in four-second periods for 11 subjects (with differing clinical conditions), analyzed a visual-verbal memory task under a short delay spontaneous recall paradigm. He did not specifically evaluate coherence, phase, peak frequency, peak amplitudes, frequency ranges above 30 Hertz, or memory under different stimiulus conditions separating out the input, immediate and delayed recall conditions.
In summary, the confusing pattern of results is due to the different tasks being employed, different subject populations and different methodologies. The most relevant to this patent are the studies by Klimesch (1993,1994, 1996, 1997) who has discovered the importance of the alpha frequencies, theta relative power and desynchronization patterns to memory performance. There is minimal emphasis in his analysis upon the issues of coherence and phase.
Regarding the third area of research in the area of coherence relationships, Busk, J., & Galbraith, G. C., (1975) demonstrated that coherence increases with the difficulty of the task, while practice reduces coherence as a result of a decrease in task difficulty.
Shaw, J. C., O'Connor, P., Ongley, C. (1977) were able to show that spatial and arithmetic task produces an increase in interhemispheric coherence in a right-handed population.
Gasser, T., Jennen-Steinmetz, C., & Verleger, T. (1987) were able to show in a visual matching task there is a marked increase in interhemispheric coherence in children.
Corsi-Cabrera, M., Gutierrez, S., Ramos, J., & Arce, C. (1988) found increased interhemispheric coherence during unsuccessful cognitive task performance (in the beta band for verbal and visual tasks and in the alpha and theta bands for a mixed task) employing the P3-P4 locations. They summarized some of the literature in the area of coherence noting that coherence increases have been observed in spatial tasks, tasks demaniding high levels of arousal, continuous movement tasks and during human communication and is inversely related to field dependence. Field dependence is a measure of cognitive style with field dependence related to more negative type personality characteristics.
Weiss, S., & Rappelsberger, P. (1998) with a sample size of 16 tried to see if "1--some frequency bands show power and coherence changes only due to the modality of presented stimuli (auditory vs. visual) and 2--if other bands show modality independent effects which should reflect real cognitive-linguistic differences between word classes (either concrete and abstract nouns)." (p. 33) Their results showed that the alpha1 band (8-10 Hz) revealed no difference between word classes (concrete vs. abstract nouns) but did demonstrate an influence of modality of stimulus presentation in that during memorization of auditorily presented nouns compared to rest alpha1 amplitudes decreased at left and right temporal electrodes. This finding was in contrast to all other electrode positions, which showed increases in amplitude. During the memorization of visually presented nouns all electrodes showed alpha1 desynchronization, mostly in the posterior regions. In terms of coherence and alpha1 changes, the auditory condition produced intrahemispheric coherence increases but during visual processing there was a coherence decrease except between central and temporo-cential electrodes. During the auditory noun processing both hemispheres showed increased coherence changes, especially in the frontal and central region. In the visual noun processing the interhemispheric coherences mainly increased in the posterior regions. There were no differences in the comparison of concrete versus abstract nouns within the alpha1 band. However, concrete nouns tended to show higher coherences within both modalities.
The only modality independent different between concrete and abstract noun processing were found in the delta (1-4 Hz), theta (5-7 Hz), and beta-1 (13-18 Hz) band at the left frontal electrodes with increased coherences for the concrete nouns. They also noted better recall (35.5%) for the concrete nouns versus 22% for the abstract nouns.
Previous research (Weiss, S., & Rappelsberger, P. (1996) had indicated higher number of coherences between different brain regions fori auditorily presented concrete nouns compared to abstract nouns in the beta1 frequency (13-18 Hz) and no differences in the alpha1 frequency (8-10 Hz).
In summary, activation conditions will increase coherences. Particular tasks will produce differences in coherence patterns, with increased coherences sometimes causing decrements in location (short posterior connections).
With regard to the research area where both activity and connectivity are simultaneously measured, Tucker, D. M., Dawson, S. L., Rothi, D. L., Penland, J. G., (1985) studied two individuals over several months on two cognitive tasks (with a 8 channel EEG) to determine if there were a characteristic pattern of activation which was stable over time. They found consistent changes in spectral information over the anterior left hemisphere during the word fluency task in terms of relative power and coherence measures. The specifics of the findings are not important for this discussion, as they are complex and represent only two subjects.
Corsi-Cabrera, M., Herrera, P., & Malvido, M. (1989) in summarizing the relationship between power and coherence across a number of studies noted that changes in coherence occur independently from changes in EEG power.
Shepard, W. D., (1990) was able to demonstrate that the coherence values of alpha in the left posterior parietal and right hemisphere predicted speed of response in a lexical decision task. There were no effects of relative power variables (2-30 Hz range).
Inouye, T., Shinosaki, K., Iyama, A., & Matsumoto, Y. (1993) (N=11) measured activation and connection issues (N=10) during mathematical tasks employing all of the 10-20 system placements and examined up to 50 Hz with a frequency resolution of 0.78 Hz. Subjects were instructed to serially subtract 7 from 1000 for 2 minutes with eyes closed. They found specific patterns of activation (left temporo-central-parietal regions) and connectivity (conceptualized as directional EEG) from the same region and within the frontal regions (especially left temporal and mid frontal)
Thornton, K., (1996) (N=3) was able to demonstrate diferences in phase, coherence and activation patterns to effective auditory memory recall. The pattern of results indicated that increases in phase and coherence are associated with better recall. As the results are complex, sample size small and this patent application represents a more refined analysis with a greater number of subjects in similar conditions, the specific results of that experiment will not be presented.
Benham, G., Rasey, B. A., Lubar, J. F., Frederick, J. A., Zoffuto, A. C. (1998) reported on the differences in power spectra and coherence in terms of subjective levels of engrossment in an auditory listening condition (listening to paragraphs). They found increased mean power in the theta (4-8 Hz) and beta1 (13-21 Hz) hands during engrossed states. There were significant increases in theta coherences from the FP1 position to F7 and T3 and from the O2 location to F4,C4,T4, & P4. Increases in alpha (8-13 Hz) coherence were evident in the Fp1-F7 relationships and T3-O1 relationships. Significant decreases in coherence were observed in the Fp2-C4 relationship.
The pattern of resuIts indicates that increased coherences yield better performance and that there is no significant relationship between activation variables and coherence variables.
In the area comprising analysis of difference in activation to success in performance, Gale, A., Davies, I., Smallbone, A. (1978) (N=21) visually presented subjects with 9 digit strings to memorize. Subjects who recalled well were more activated in the left hemisphere and the level of EEG activity (7-20 Hz) in the early trials (left hemisphere) predicted overall recall. The amplitudes were associated with superior recall when the information was new, but decreased amplitudes when the subjects had practiced more. Only posterior leads were employed (occipital). Earle, J. B. (1988) (N=20) found increasing mathematical task difficulty (activation conditions) led to changes in parietal amplitude asymmetries in the alpha band with the locations under investigation (P3, P4, T4, and T6 referenced to Cz). He found performance differences related to these asymmetries (left greater than right) with greater asymmetries related to better performance. He also found that right temporal activation was significantly related to overall performance as well as high mean alpha frequencies. In the verbal activation condition, he found a decreasing alpha frequency with improved performance in the parietal regions as the difficulty of the task increased.
In the fourth area involving rehabilitation efforts toward cognitive functioning, the rehabilitation efforts of Lubar, J. O., & Lubar, J. F. (1984), Tansey, M., (1991) & Othmer, S. & Othmer, (1992) (N=14) have been directed towards the specific clinical problems of Attention Deficit Disorder and Learning Disability. The results have indicated improvement in cognitive functioning in terms of IQ scores (15 to 25 points) and school performance (as well as attitudinal and behavioral changes). However, the specific link between successful cognitive task pertormance and QEEG variables is inferred from the improvement and not demonstrated empirically. The locations employed have focused on the C3-Cz positions predominantly and have augmented beta activity (13-21 Hz) and inhibited theta activity (4-8 Hz).
Thompson, L., & Thompson, M., (1985) were able to demonstrate significant improvement with Asperger's syndrome by providing feedback which reduced theta activity (4-8 Hz) and increased beta (13-15 Hz & 16-20 Hz) activity. Improvements were noted in social interaction, decreased use of medication and improvement in academic functioning and on standardized tests.